1. Field of the Invention
The present invention relates generally to an image forming machine and, more particularly, to a media handling system for maintaining a top of a media stack within a given range of pick positions during feeding of sheets one at a time from the stack top.
2. Description of the Related Art
To feed a large amount of media sheets from a media handling system to an image forming machine without interruption, there is a first operational requirement to maintain the top of the large stack of media sheets, for instance, a stack of greater than 500 sheets, within a given range of pick positions in which a pick mechanism supported on the frame of the machine operates. This will enable a feed roll of the pick mechanism to reach and individually pick the top sheet from the stack and feed it to the image forming machine or to an intermediate module that feeds the picked sheet to the machine. To accommodate this first operational requirement in the media handling system a platform typically is provided in a movable bin. The platform is mounted to the bin so as to undergo vertical movement relative to the bin and toward and away from the pick mechanism located above the bin. Also, there is a second operational requirement that the bin itself be mounted to the frame of the machine to undergo horizontal sliding movement out of and into the machine between a reload position located externally of the frame and the sheet pick position located internally of the frame in order to periodically replenish the supply of media sheets stacked on the platform in the bin. Further, there is a third operational requirement that the components of the media handling system accommodate a range of different media types and weights.
It can easily be realized that the first two operational requirements could come into conflict when the bin needs to be moved from the internal sheet pick position to the external sheet reload position. The top of the stack on the platform or the platform itself when disposed within the given range of pick positions in which the pick mechanism operates may be close enough to cause interference with components of the pick mechanism should the bin be moved away from the frame of the machine without first relocating the platform downward away from the pick mechanism. Thus, there is a need to ensure that the platform will be maintained within a desired range of elevations or levels to keep the top of the stack within the given range of pick positions that the pick mechanism operates in while at the same time ensure that the platform will be automatically lowered to remove the top of the stack or platform below the range of pick positions wherever the bin is moved to the external reload position away from the pick mechanism of the machine. In addition, it can easily be realized that this need must be resolved in a way that allows the system to satisfy the third operational requirement, the applicability of its components to an acceptable range of different media types and weights.
A resolution of this need could readily be found if there were only modest limitations on the cost of mechanisms that could be used to fulfill all of these operational requirements. However, given the competitive market environment that exists in the field of image forming machines, rather stringent cost limitations continue to be imposed on product innovations. Feasible solutions are only those that add minimal cost to these machines while still accommodating a range of different media types and weights. Some prior art approaches are applicable only to machines that are dedicated to a single or very limited range of media types and weights. Other prior art approaches require the use of high-capacity motors with built-in power supplies that are too high in cost to implement and so are not considered to offer feasible solutions that meet these operational requirements in the current competitive environment.
Thus, there is still a need for an innovation that will resolve the potential conflict between the aforementioned operational requirements under the restrictive cost limitations imposed on product innovations.